Recruiting code: JBAZNYW5

Remember that you can only be recruited before paying for your first subscription (the initial free 30 days you're given after purchase don't count and you can be recruited while on that trial as long as you have not yet paid for a subscription).

Recruitment codes are redeemed over at the Mogstation (https://sqex.to/Msp), scrolling down slightly until you find the Enter Recruitment Code button, you can redeem it over there.

After being recruited, you will receive some rewards when you pay for your first subscription. Namely, you get 99 Aetheryte Tickets (99 free teleports), the Friendship Circlet (a headgear piece that gives you an XP boost if you're under level 25), and a couple other bells and whistles.
You can find the official page for this campaign over here: https://na.finalfantasyxiv.com/lodes...riend_recruit/
The rewards for being recruited are shown over at the bottom of the page.
Hope you have a good time!